Ultrasonic cutting blade with cooling liquid conduction

ABSTRACT

An ultrasonic surgical tool comprises a substantially planar blade body having a pair of opposed lateral surfaces and a cutting edge. A shank integral on a distal side with the blade body is provided at a proximal side with a connector for operatively linking the blade to a source of ultrasonic mechanical vibrations. The blade body is provided in at least one of the lateral surfaces with a shallow recess which is nearly coextensive with that lateral surface. The blade body has a raised rim surrounding and defining the recess, the rim being narrow on the three sides between the recess and the cutting edge.

FIELD OF THE INVENTION

This invention relates to an ultrasonic tool. More particularly, thisinvention relates to an ultrasonic cutting blade. The blade isparticularly useful in a surgical application to cut tissue such ascartilage and bone. The present invention is also directed in part to anassociated surgical method.

BACKGROUND OF THE INVENTION

In the field of orthopedics, the cutting of living bone is aprerequisite for many procedures. Such procedures include thereconstruction of damaged tissue structures due to accidents, thegrafting of healthy bone into areas damaged by disease, or thecorrection of congenital facial abnormalities like a receding chin line.Over several centuries, these tasks were performed through theutilization of devices called bone saws.

Traditional bone saws are categorized into several basic categories.Hand powered saws or drills are just that, hand held devices whichrequire the operator to move the device in a fashion similar to thatused for carpentry tools. Powered devices, whether electric orpneumatic, are of either the reciprocating or rotary type. Thereciprocating devices use a flat, sword like blade where the back andforth motion is provided by a motor instead of the hand. The rotarydevices use a rotating motor to spin a drill bit or a blade that hasteeth arranged around its circumference similar to a table saw blade.All of these traditional bone saws are used today in medical proceduresaround the world.

While traditional saws are functional, they have many disadvantages.With either the band or reciprocating saws, for instance, it is not easyto initiate and direct a cut. A cut must start from an edge or,alternatively, a starting hole must be used. To create a starting hole,a drill or similar instrument is operated to bore into the bone.Subsequently, a cutting blade is inserted into the bored hole. The usercan then proceed to cut. Alternatively, a rotary type blade may be used.However, when a rotary blade is used, the cut must follow a relativelystraight path to prevent the blade from binding in the cut. With allblades the ability to create a curved or compound angle cut is extremelylimited by the blade chosen. The relatively thick blades have a widekerf, so that a significant thickness of the viable bone is lost in thecutting procedure. Physicians would like this width to be as thin aspossible in most procedures where reconstruction is necessary.

Above all, the relatively slow linear or tangential speeds ofconventional bone saw blades coupled with the teeth necessary forcutting result in high frictional losses, which becomes manifested asheat. Heat will cause necrosis of the tissue if the bone temperaturesreach 47° C. for more than a few seconds. When tissue necroses, the bonerecedes after the surgery as the necrotic bone is overgrown. During suchnatural post-surgical tissue developments, the thickness of the cuts inthe bone actually increases. The bone rescission process must becomplete before healing can begin. To prevent the shortening of thelength of the bone, metal plates and screws are used to fix the bonefragments in proper position. All of these factors obviously lead toincreased operative time, and more importantly, to dramaticallyincreased healing time, since the bone must knit across a greater span.Some studies have shown the strength of the bone to be effectednegatively as well

When an upper or lower jaw is to be cut in elective surgery, the heatingeffect of traditional saws requires even more extraordinary interventionto prevent damage. Cutting the jaw between the teeth will cause loss ofteeth if the bone is damaged or does not heal quickly. To prevent thetooth loss, the teeth must be spread apart preoperatively;

sometimes forcing the patient to wear braces for up to 6 months beforethe operation can take place. In these cases, the costs and patientdiscomfort increases dramatically.

To limit the tissue temperature rise in an attempt to reduce necrosis,some traditional surgical saws provide cooling liquid to the surgicalsite. See, for instance,

U.S. Pat. No. 4,008,720 to Brinckmann et al. These devices typicallyintroduce coolant into spaces between segments on the cutting edge orrely on spray methods to flood the cutting site with fluid. Anothertechnique employed by clinicians is to make very light cuts and increasethe time between passes of the tool. Coupled with irrigation of thearea, bone temperature rise is reduced measurably. Of course, thistechnique increases operative time and clinician fatigue.

Several researchers have proposed the use of ultrasonic tools for boneseparation. The use of ultrasonic surgical instruments for cuttingthrough various tissues is well known. While these devices are superiorto the traditional saws in several aspects such as reduced kerf size,reduced noise, and superior ability for making complex geometric cuts,the temperature rise in bone due to frictional heating at theblade/tissue interface is still a significant problem. The problem isexacerbated with the use of ultrasonics due to the rapid motion involvedas compared to that of traditional reciprocating saws. Some designershave tried to reduce heating by modifying the cross-section of thecutting blade. U.S. Pat. No. 5,188,102 to Idernoto, U.S. Pat. No.4,188,952 to Loschilov, and U.S. Pat. No. 5,261,922 to Hood all showdesigns for cutting which have modified cross sections to reducefrictional heating.

Several ultrasonic devices have provided cooling to the cutting bladewith varied degrees of success. U.S. Pat. No. 4,823,790 to Alperovich etal. shows a design for a cryogenically cooled scalpel blade. However,this design may actually damage viable tissue by freezing. In addition,this design does not provide any coolant to surrounding tissue not indirect contact with the blade.

U.S. Pat. Nos. 5,205,817, 5,188,102, and 4,832,683 all to Idemoto showexamples of ultrasonic instruments with provisions for fluid cooling.These instruments, however, either do not provide optimal coolant flowwhere it is needed, mainly at the cutting portion of the blade, or forones that do provide coolant at the tip, they interrupt the cutting edgewith holes for the coolant. An interrupted, uneven cutting edge hindersmanipulation and makes it difficult to guide the blade on the bonesurface.

One phenomenon associated with ultrasonic tooling which acts to hinderthe beneficial effects of irrigating the operative site is ultrasonicatomization. When an ultrasonically vibrating body is brought intocontact with fluid, that fluid is broken into small droplets, which havea size inversely proportional to the frequency of vibration. In otherwords, the higher the frequency, the smaller and more mobile the liquiddrop. Droplets created by ultrasonic vibrations can be very small insize, with some being less than 1 micron in diameter. This phenomenon iswell known to the art. In fact, many devices intended to atomize liquid,such as room humidifiers, medical nebulizers, and industrial spraynozzle are based upon this principle. In the operating theater, however,the presence of nebulized particles is not appreciated, since theseparticles may contain viral or bacterial agents. Also, some of the fluidwill be atomized before reaching the operative site, reducing thecooling efficiency. An effective way to insure the liquid transport isneeded.

U.S. Pat. No. 6,379,371 discloses an ultrasonic surgical blade withcooling, which has a blade body with a smooth continuous cutting edgeand a shank connected at one end to the blade body and operativelyconnectable at an opposite end to a source of ultrasonic vibrations. Theshank is provided with an axially extending bore for the conveyance ofcooling fluid to the cutting edge, while the blade body is provided withan axially extending through-slot communicating at one end with thebore. The blade body is preferably provided at an end opposite the shankwith a recess communicating, with the bore for distributing fluid fromthe slot towards the cutting edge. The recess may have a configurationthat parallels at least a portion of the cutting edge. Where the cuttingedge is circular and the blade body has a planar surface between thefluid distribution guide surface and the cutting edge, for instance, therecess has a fluid distribution surface inclined with respect to theplanar blade surface and extending along a circular arc.

SUMMARY OF THE INVENTION

The present invention aims to provide an improved ultrasonic tool orprobe which has an improved cooling capability. An ultrasonic tool orprobe in accordance with the invention may particularly take the form ofultrasonic cutting blade which allows thin kerf cuts, does not requirepredrilled holes for cutting, allows complex geometric cuts, has acontinuous cutting surface, and provides for liquid irrigation atprimarily the blade/tissue interface. More specifically, the presentinvention pertains to an ultrasonically vibrated cutting blade with animproved provision for delivery of a cooling medium for reducing andlimiting thermal damage to living tissue. The present inventionspecifically targets the application of cutting viable bones in surgery,although the device is not exclusive to this application.

An ultrasonic surgical tool comprises, in accordance with the presentinvention, _(a) substantially planar blade body having a pair of opposedlateral surfaces and a cutting edge. A shank integral on a distal sidewith the blade body is provided at a proximal side with a connector foroperatively linking the blade to a source of ultrasonic mechanicalvibrations. The blade body is provided in at least one of the lateralsurfaces with a shallow recess, which is nearly coextensive with therespective lateral surface. The blade body has a raised rim surroundingand defining the recess, the rim being narrow on the three sides. On thefourth, proximal, side of the recess, a proximal portion of the bladebody, which merges with the shank, bounds the recess.

The blade body is preferably provided with a through hole in the recess.The through hole extends between the lateral surfaces of the blade bodyand enables liquid flow from the recess to an opposing side of the bladebody.

The shank is preferably provided with a bore or channel having an outletcommunicating with the recess, thereby enabling liquid flow into therecess from a source connected to the channel.

The through hole may extend in a proximal direction to a proximal end ofthe recess or recesses. In that case the through hole is continuous withthe bore or channel a_(t) the outlet thereof.

In a preferred embodiment of the present invention, the recess is one oftwo recesses each provided in a respective one of the lateral bladesurfaces, each recess being defined by a surrounding rim. The throughhole enables liquid communication between the recesses.

Each of the recesses occupies a major portion of the respective lateralsurface. Each recess is defined in substantial part by a shallow wallformed by the rim on three ides and the proximal portion of the bladebody on the proximal side. Where the shank is provided with aliquid-delivery bore or channel, the bore or channel may communicatewith each recess, either via separate outlet holes or via a singleoutlet opening onto both lateral blade surfaces.

Pursuant to another feature of the present invention, the blade body andthe recess are elongate and the through hole is an elongate narrowopening, i.e., a slot.

An ultrasonic surgical tool comprises, in accordance with the presentinvention, a substantially planar blade body having a pair of opposedmajor faces and a peripheral flange extending along three sides of theblade body. The flange defines a recess in at least one of the opposedmajor faces. The recess is substantially coextensive with the bladebody, that is, occupies nearly all of the respective major face of theblade body. At least a portion of the flange has a cutting edge orsurface. A shank integral on a distal side with the blade body isprovided at a proximal side with a connector for operatively linking theblade to a source of ultrasonic mechanical vibration.

Other features of the present invention are described above, namely, theprovision of two recesses each on a respective major surface of theblade body, the slot in the blade body, the liquid delivery bore orchannel and the arrangement of liquid outlets in the recess or recesses.Where there are two recesses on opposing sides of the blade body, eachof the recesses is defined on three sides by the flange. In that case,the flange projects in opposite directions from the place of the bladebody orthogonally thereto. The proximal end of the blade body has athickness equal to that of the flange and defined the recess or recesseson a proximal side thereof.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic isometric view of an ultrasonic surgical tool inaccordance with the present invention.

FIG. 2 is a schematic cross-sectional view taken along line II-II inFIG. 1, showing a modified design of the ultrasonic surgical tool on asmaller scale.

FIG. 3 is a schematic partially cross-sectional view taken along lineII-II in FIG. 1 and shows the modified design of FIG. 2.

FIG. 4 is a schematic cross-sectional view similar to FIG. 2, showinganother modified design on a reduced scale.

FIG. 5 is a schematic partial cross-sectional view similar to FIG. 3,showing the modified design of FIG. 4.

FIG. 6 is an isometric view of another ultrasonic surgical tool inaccordance with the present invention.

FIG. 7 is a top plan view of the ultrasonic surgical tool of FIG. 6.

FIG. 8 is a side elevational view of the ultrasonic surgical tool ofFIGS. 6 and 7.’

DETAILED DESCRIPTION

As depicted in FIGS. 1-3, an ultrasonic surgical tool 10 comprises asubstantially planar blade body 12 having a pair of opposed major sides(not separately enumerated) provided with recessed surfaces 14 and 16and a flange 18 extending around the recessed surfaces 14 and 16 onthree sides thereof to define therewith a pair of opposing shallowrecesses 20 and 22. Flange 18 extends away from recessed surfaces 14 and16, generally orthogonally or perpendicularly to the planes (notseparately designated) of those surfaces. Flange 18 serves as a rim orsidewall for each recess 20 and 22. Recesses 20 and 22 are delimited ona proximal side of blade body 12 by respective sidewalls 24 continuouswith flange 18 and formed by a proximal blade body portion 26 thatmerges with a tapered portion 28 of a blade shank 30.

Blade body 12 accordingly has a pair of opposed lateral surfaces 32 and34 that are planar outer surfaces of proximal blade body portion 26 andflange 18. Recessed surfaces 14 and 16 are parallel to and inwardlyspaced from lateral surfaces 32 and 34.

Recesses 20 and 22 occupy nearly the entirety of blade body 12 along theopposite major sides thereof. Flange or rim 18 is a narrow stripsurrounding the recesses 20 and 22. An outwardly facing surface 36 offlange 18 includes a cutting edge or surface, at least at a distal tip38 of blade body 12 and optionally along one or both lateral sides 40and 42 of blade body 12.

Shank 30 is integral on a distal side with blade body 12 and is providedat a proximal side with an externally threaded connector 44 foroperatively linking the blade to a source (not shown) of ultrasonicmechanical vibrations. Typically, connector 44 screws into a receptacleon a handpiece, the handpiece housing a piezoelectric crystal stack thatgenerates ultrasonic vibrational energy in response to an electricalwaveform input of an ultrasonic frequency.

Blade body 12 is provided with a through hole 46 extending betweenrecessed surfaces 14 and 16 and providing a path of fluid communicationbetween recesses 20 and 22.

Shank 28 is provided with a bore or channel 48 having, in one embodimentof the ultrasonic surgical tool 10, a single outlet port 50communicating directly with one recess 20. Bore or channel 48 isconnectable to a source of irrigant or cooling liquid and guides theliquid into recess 20 via outlet port 50. The irrigant or cooling liquidenters the other recess 22 via through hole 46.

As shown in FIGS. 2 and 3, bore or channel 48 may include a centralaxial upstream section 52 and a pair of branching downstream sections 54and 56 terminating in respective outlet ports 58 and 60. Outlet ports 58and 60 are located in proximal sidewalls 24 of recesses 20 and 22.Recesses 20 and 22 therefore each receive irrigant or cooling liquidfrom bore or channel 48 via respective outlets 58 and 60. Through hole48 may be eliminated but is preferably retained for pressureequalization and the resulting enhanced fluid flow.

As depicted in FIGS. 4 and 5, bore or channel 48 may extend distally toan outlet opening 62 in sidewalls 24 of recesses 20 and 22. Recessedsurfaces 14 and 16 define a web or septum (not separately designated)that bifurcates outlet opening 62 to form a pair of D-shaped outputports 64 and 66.

Recesses 20 and 22 allow for improved irrigant delivery at a bladetissue interface, both along lateral surfaces 32 and 34 and cutting edge38, as well as along lateral surfaces 68 and 70 of flange or sidewallrim 18. Lateral surfaces 68 and 70 may serve as additional cutting edgesof blade body 12.

As depicted in FIGS. 6-8, an ultrasonic surgical tool 110 comprises asubstantially planar blade body 112 having a pair of opposed major sides(not separately enumerated) provided with recessed surfaces 114 and 116and a flange or shoulder 118 extending around the recessed surfaces 114and 116 on three sides thereof to define therewith a pair of opposingshallow recesses (not separately designated). Flange 118 is staggeredaway from recessed surfaces 114 and 116, generally orthogonally orperpendicularly to the planes of those surfaces. Flange 118 serves as arim or sidewall that together with recessed surfaces 114 and 116 definedthe recesses. The recesses are delimited on a proximal side of bladebody 12 by respective sidewalls 124 continuous with flange 118 andformed by a tapered portion 128 of a blade shank 130.

Blade body 112 accordingly has a pair of opposed lateral surfaces 132and 134 (FIG. 8) that are planar outer surfaces of flange 118 and thatare continuous with respective sloped outer surfaces (not designated) oftapered shank portion 128. Recessed surfaces 114 and 116 are parallel toand inwardly spaced from lateral surfaces 132 and 134.

Recessed surfaces 114 and 116 and accordingly the associated recessesoccupy nearly the entirety of blade body 112 along the opposite majorsides thereof, excepting a beveled cutting edge 126 that arcs about adistal tip 138 of blade body 112 and partially along a distal end oflateral sides 140 and 142 of blade body 112. Along a distal end segmentof blade body 112, flange or rim 118 is a narrow strip 118′ sandwichedbetween the recessed surfaces 114 and 116 and beveled cutting edge 126.On a proximal side of the blade body 112, flange or rim 118 is a broaderstrip 118″ extending along the lateral sides 140 and 142 of blade body112

Shank 130 is integral on a distal side with blade body 112 and isprovided at a proximal side with an externally threaded connector 144for operatively linking the blade to a source (not shown) of ultrasonicmechanical vibrations. Typically, connector 144 screws into a receptacleon a handpiece, the handpiece housing a piezoelectric crystal stack thatgenerates ultrasonic vibrational energy in response to an electricalwaveform input of an ultrasonic frequency.

Blade body 112 is provided with an elongate through hole or slot 146extending between recessed surfaces 114 and 116 and providing a path offluid communication between the recesses on opposing major sides ofblade body 112.

Shank 128 is provided with a bore or channel 148 having a single outletport 150 communicating directly with elongate through hole or slot 146as well as the opposed recesses on the opposing major sides of bladebody 112. Through hole or slot 146 extends in the proximal direction allthe way to sidewalls 124 and is continuous with bore or channel 148 atoutlet port 150. Bore or channel 148 is connectable to a source ofirrigant or cooling liquid and guides the liquid into through hole orslot 146 and the opposed shallow recesses via outlet port 150.

Recessed surfaces 114 and 116 allow for improved irrigant delivery at ablade tissue interface, both along lateral surfaces 132 and 134 andcutting edge 126. Blade body 112 may be formed at a distal end of slot146 with a beveled or sloped extension 152 facilitating irrigantmovement from slot 146 towards the portion of cutting edge 126 at distaltip 138, so that the irrigant is distributed along the distal tip.

Although the invention has been described in terms of particularembodiments and applications, one of ordinary skill in the art, in lightof this teaching, can generate additional embodiments and modificationswithout departing from the spirit of or exceeding the scope of theclaimed invention. For instance, beveled cutting edge 126 may beprovided in the embodiment of FIGS. 1-3 and extend nearly along theentire sides 40 and 42. Accordingly, it is to be understood that thedrawings and descriptions herein are proffered by way of example tofacilitate comprehension of the invention and should not be construed tolimit the scope thereof.

What is claimed is:
 1. An ultrasonic surgical tool comprising: asubstantially planar blade body having a pair of opposed lateralsurfaces; and a shank integral on a distal side with said blade body andprovided at a proximal side with a connector for operatively linking theblade to a source of ultrasonic mechanical vibrations, said blade bodybeing provided in at least one of said lateral surfaces with a shallowrecess nearly coextensive with said one of said lateral surfaces, saidat least one of said lateral surfaces forming a raised rim surroundingand defining said recess, said rim being narrow on a distal side of saidblade body and along two lateral sides of said blade body.
 2. Thesurgical tool of claim 1 wherein said blade body is provided in saidrecess with a through hole enabling liquid flow from said recess to anopposing side of said blade body.
 3. The surgical tool of claim 2wherein said shank is provided with a bore or channel having an outletcommunicating with said recess and enabling liquid flow into said recessfrom a source connected to said channel.
 4. The surgical tool of claim 3wherein said recess is one of two recesses each provided in one of saidlateral surfaces, each defined by a surrounding rim, said through holeenabling liquid communication between said recesses.
 5. The surgicaltool of claim 4 wherein each of said recesses occupies a major portionof the respective major side of said blade body, the rim of each of saidrecesses defining a shallow sidewall extending parallel to said distalside and said lateral sides of said blade body.
 6. The surgical tool ofclaim 3 wherein said through hole extends to a proximal end of saidrecess and is continuous with said bore or channel.
 7. The surgical toolof claim 2 wherein said blade body and said recess are elongate and saidthrough hole is a slot.
 8. The surgical tool of claim 1 wherein saidshank is provided with a bore or channel having an outlet communicatingwith said recess to enable liquid flow into said recess from a sourceconnected to said channel.
 9. The surgical tool of claim 8 wherein saidthrough hole extends to a proximal end of said recess and is continuouswith said bore or channel at said outlet.
 10. The surgical tool of claim1 wherein said recess is one of two recesses each provided in arespective major side of said blade body, each of said recesses beingdefined by a surrounding rim or wall, each of said recesses occupying amajor portion of the respective major side of said blade body.
 11. Anultrasonic surgical tool comprising: a substantially planar blade bodyhaving a pair of opposed major faces, said blade body having aperipheral flange extending along three sides of said blade body anddefining a recess in at least one of said major faces, said recess beingsubstantially coextensive with said blade body, at least a portion ofsaid flange having a cutting edge or surface; and a shank integral on adistal side with said blade body and provided at a proximal side with aconnector for operatively linking the blade to a source of ultrasonicmechanical vibration.
 12. The surgical tool of claim 11 wherein saidblade body is provided with at least one through hole in said recess,said through hole extending between opposed major faces and enablingliquid flow from said recess to an opposing one of said major faces. 13.The surgical tool of claim 12 wherein said shank is provided with a boreor channel having an outlet communicating with said recess to enableliquid flow into said recess from a source connected to said channel.14. The surgical tool of claim 13 wherein said recess is one of tworecesses on said major faces of said blade body, each of said recessesbeing defined on three sides by said flange, said flange projecting inopposite directions from said major faces orthogonally thereto, said atleast one through hole enabling liquid communication between saidrecesses, each of said recesses occupying a substantial portion of therespective one of said major faces.
 15. The surgical tool of claim 14wherein said blade body has a proximal portion merging on a proximalside with said shank and bounding said recess on a distal side, saidproximal portion of said blade body having a width substantially equalto a width of said flange.
 16. The surgical tool of claim 14 whereinsaid blade body and said recess are elongate and said at least onethrough hole is a slot.
 17. The surgical tool of claim 13 wherein saidshank is provided with a bore or channel having an outlet communicatingwith said recess, thereby enabling liquid flow into said recess from asource connected to said bore or channel.
 18. The surgical tool of claim17 wherein said recess is one of two recesses in respective ones of saidmajor faces of said blade body, each of said recesses being defined onthree sides by said flange, said flange projecting in oppositedirections orthogonal to said lateral surfaces, said at least onethrough hole enabling liquid communication between said recesses, eachof said recesses occupying a major portion of the respective one of saidmajor faces, said recesses being bounded and defined on a proximal sideby a proximal portion of said blade body merging on a proximal side withsaid shank, said proximal portion of said blade body having a widthsubstantially equal to a width of said flange.
 19. The surgical tool ofclaim 17 wherein said at least one through hole extends to a proximalend of said recess and is continuous with said bore or channel at saidoutlet.
 20. The surgical tool of claim 13 wherein said recess is one oftwo recesses on opposing sides of said blade body, each of said recessesbeing defined on three sides by said flange, said flange projecting inopposite directions orthogonal to a plane of said blade body.